Torque compensating mechanism for boat drives

ABSTRACT

A tiltable propeller housing of a vessel is provided with a mechanism for counteracting undesired torques or moments acting on the tiller or rudder when the boat is in motion. The housing has a power transmitting intermediate shaft, around which only the lower portion of the housing is able to rotate. Pressure means forming part of a tilting and trimming means are mounted between the stern and the housing, and the end of the pressure means facing the housing is mounted for movement generally fore and aft in the non-rotatable upper portion of the housing, the pressure means engaging, either directly or indirectly, a cam located on the rotatable housing portion. The cam laterally displaces the contact point of the bearing surface on which the propeller pressure is taken up by the pressure means thereby providing a steering moment which compensates for undesired torque on the rotatable housing portion.

United States Patent [191 Bergstedt r111 3,857,357 r451 Dec. 31,1974

[75] Inventor: Karl Abdon Bergstedt, Gothenburg,

. Sweden [73] Assignee: AB Volvo Penta, Gothenburg,

Sweden [22] Filed: Apr. 17, 1973 [21] Appl. No.: 352,063

[52] US. Cl 115/41 R [51] Int. Cl B63h 5/12 Field of Search. 115/34 R, 34 A, 41 R, 41 HT,

[56] References Cited UNITED STATES PATENTS 3,024,759 3/1962 Byrd 115/41 R 3,171,382 3/1965 Bergstedt...

3,626,467 12/1971 Mazziotti 115/41 HT Primary Exa'miner--Trygve M. Blix Assistant Examiner-Stuart M. Goldstein Attorney, Agent, or FirmGeorge H. Baldwin; Arthur G. Yeager [5 7 ABSTRACT A tiltable propeller housing of a vessel is provided with a mechanism for counteracting undesired torques or moments acting on the tiller or rudder when the boat is in motion. The housing has a power transmitting intermediate shaft, around which only the lower portion of the housing is able to rotate. Pressure means forming part of a tilting and trimming means are mounted between the stern and the housing, and the end of the pressure means facing the housing is mounted for movement generally fore and aft in the non-rotatable upper portion of the housing, the pressure means engaging, either directly or indirectly, a cam located on the rotatable housing portion. The cam laterally displaces the contact point of the bearing surface on which the propeller pressure is taken up by the pressure means thereby providing a steering moment which compensates for undesired torque on the rotatable housing portion.

22 Claims, 6 Drawing Figures PATENTED UEC3 1 I974 SHEET 1 OF 4 PATENTEU ma] I974 sum 2 or 4 FIGJb 1 PATENFEB W3? W4 SHEET 3 OF 4 TORQUE COMPENSATING MECHANISM FOR BOAT DRIVES The present invention relates to a torque compensating mechanism for a propeller housing suspended from the stern of a boat and arranged for tilting in a vertical plane. Propeller housings of the type comtemplated have a power transmitting intermediate drive shaft which extends downwardly when the propeller housing is in its operative position. The housing has a portion which is rotatable around the shaft and another portion which is non-rotatable relative to said shaft. A pressure means forming part of a tilting and trimming arrangement is mounted between the stern of the boat and the propeller housing. With propeller housings of this type,

' such as for example that described in the Swedish Patent No. 220,881 (British Patent No. 1,161,105), moments are created which attempt to turn the rotatable portion of the housing and thus also the propeller shaft.

There are at least two basic reasons for these moments. One moment is created by the driving force transmitted from the intermediate shaft to the propeller shaft through a gearing. The other moment arises due to the fact that the propeller rotates in an upwardly flowing stream of water created by the stern of the boat moving through the water the stream of water forming a substantial angle to such propeller shaft in a vertical plane through the propeller shaft. Both of these moments must be compensated by applying a counter force to the tiller or rudder, which can be very fatiguing and inconvenient in the operation of the boat.

The Swedish Patent 21 1,970 (British Patent 1,044,931) describes an arrangement for compensating for the first mentioned moment. With such an arrangement the intersecting point between the propeller and intermediate shaft lies essentially in the same plane as the pitch circle of a crown wheel mounted on the propeller shaft and forming part of the aforementioned gearing.

The U.S. Pat. No. 3,171,382 granted Marf2, 1965 the aforementioned'moments. With such mechanism a horizontal cam plate arranged on the propeller housing co-acts with a substantially vertical support shoulder mounted on'the stern transom, the contact point between the cam plate and the support shoulder being located on one side of the propeller shaft. Although such mechanism compensates for both undesired moments, it can only be used with smaller power boat units and it makes same difficult to trim.

An arrangement constructed according to the pres ent invention compensates for both moments. however, without having this latter restriction or the aforementioned disadvantages.

An object of the present invention is to provide a mechanism which when installed with propeller units of the above mentioned type compensates for undesirable torque on the rotatable portion of the propeller housing without restricting thesize of the propeller unit. Another object is to provide a mechanism which affords the aforementioned compensation while at the same time permitting hydraulic tilting and trimming of the propeller unit. A further object of the invention is to provide an arrangement which permits simple and efficient adjustment of the magnitude of the compensating steering moment.

The mechanism of the present invention fulfills these and other objects by providing that the end of a pressure means facing the propeller housing is displaceably mounted in the non-rotatable portion of the propeller housing and bears, either directly or indirectly, against a cam arranged on the rotatable portion of the propeller housing. The cam is arranged to laterally move the contact point of the support surface at which the propeller pressure is taken up by the pressure means and thereby provides a steering moment which compensates for undesired torque on the rotatable portion of the propeller housing.

The embodiment of the mechanism of the invention will be described by way of example and should not be considered restrictive to the scope of the invention. With the exemplary embodiment, the invention is applied to a drive which is also provided with an arrangement for compensating for the moment first mentioned above, i.e. an arrangement according to Swedish Patent No. 211,970 (British Patent 1,044,931). Residual moments may also occur on a drive provided with the arrangement of such patent, and the present invention is intended to compensate for such residual moments and to compensate for the moment produced by the propeller.

The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. la is a side elevational view, portions being broken away, and illustrating the upper portion of a propeller unitfor boats including an embodiment of the mechanism according to the invention;

FIG. 1b is a side elevational view illustrating the lower portion of the propeller unit shownin FIG. 1a;

FIG. 2 is a cross-sectional view taken along line II II of FIG. 1a and illustrating the cam setting means;

FIG; 3 is a sectional view taken along line IIIIII in FIG. 1a and illustrating the gearing means mounted on the suspension means;

FIGS. 4a and 4b are cross-sectionalviews taken along line IVIV in FIG. 1a and illustrating the cam and-a roller engaging the same.

The boat propeller unit is generally indicated in FIGS. Ia and lb by the reference numeral 1, having a propeller housing 3 suspended from the stern transom 2 of a boat, the housing 3 being arranged for tilting movement around a horizontal supporting shaft 4, as

.shown specifically in FIG. 3 and as indicated generally in FIG. 1a. The engine (not shown) of the boat is connected directly to a rotary shaft 5 co-acting with a gear wheel 7 forming part of the gearing means 6. The elements forming part of the gearing means 6 will be more fully understood by reference to FIG. 3. Engine power is transmitted from the shaft 5 through the gearing means 6 to a gear wheel 8 firmly connected on a downwardly extending intermediate hollow shaft 9. The en gine power is then transmitted from the intermediate shaft 9 to a propeller shaft 11 and to a propeller (not shown) mounted to such shaft 11 through gearing means 10. The propeller housing 3 has a lower portion 12 adapted to be rotated around the intermediate shaft 9, and an upper portion 13 which is non-rotatable around such shaft 9.

Mounted between the stern 2 of the boat and the propeller housing 3 is a hydraulic tilting and trimming means 14. As illustrated in FIG. 1a, the tilting and trimming means 14 may have the form of a hydraulic ram or piston and cylinder assembly. The means 14 includes a pressure means 15, which in the exemplary embodiment comprises the piston rod of the assembly. As is well known in the art, the hydraulic cylinder 21 could also be used as the pressure means, as could any other suitable element connected with the piston rod 15 or the cylinder 21. Y

The end portion 16 of the pressure means 15 facing the propeller housing 3 is connected to a piston-like body 17 which is carried by and arranged for restricted axialrnovement generally fore and aft in a cylinder-like bearing 18 arranged in the non-rotatable upper or outer portion 13 of the propeller housing 3. The body or pressure transmitting element 17 presses against a cam 19 arranged on the rotatable lower or inner portion 12 of the propeller housing 3. The end portion 16 of the pressure means 15 is connected with the piston 17 by means of a pivotal connecting means 22, whereby force transmitting or pressure element 17 constitutes a pivotally attached end portion or extension of pressure means 15. The bearing 18 is in the form of a cylinder and is arranged in and comprises a part of the non-rotatable portion 13 of the propeller housing 3. In that the axial movement of piston 17 in a forward direction is restricted, the forward portion of bearing 18 being smaller than the aftward end portion of piston 17 as seen in FIG. 1a, the housing 3 may not tilt substantially without pulling with it piston rod 15 in a direction outwardly'of. cylinder 21.-A roller 23 is rotatably journalled around a peg 24 arranged in the end portion 16' f the body 17 facing the intermediate shaft 9. The body 17 is arranged to indirectly engage the cam 19 through roller 23.

The cam 19 is attached to a cam sleeve 25 which concentrically surrounds a guide sleeve 26,. which also forms a guide means for the rotatable lower portion 12 of the propeller housing 3. The sleeves 25 and 26 are connected together by means of a spline joint comprising, in a conventional manner, axially extending lands 27 engaging corresponding grooves 28. The guide sleeve 26 is rotatably mounted in the upper portion 13 of the housing in bearings 29 and 30. The guide sleeve 26 is not normally rotatable relative the lower portion 12 of the housing, butherein means are provided to mitting limited relative movement between guide sleeve 26 with its attached cam 19 and lower housing portion 12 includes settable means in the form of two spaced screws 34 threadedly engaged within spaced openings 37 which are located in the housing 12, screws 34 having portions 35 projecting into recesses 36 which are formed in the guide sleeve 26. The recesto the lower portion 12 of the propeller housing 3. Both ses 36 are arranged to permit a predetermined degree of rotation of the guide sleeve 26 in relation to the position. illustrated in FIG. 2 and with respect to lower housing portion 12. When one of the screws 34 is screwed out, the other screw is screwed in a corresponding amount or degree to appropriately set the posed toward respective ones of the two threaded openings 37 and so disposed that when either one of the recessed portions 36 moves toward its respective one of the openings 37, as-a result of relative rotation between sleeve 26 and housing portion 12, the other recessed portion 36 moves away from the other of openings 37. Respective setting screws 34 contacting the respective opposed portions of the sleeve member may be usedto adjust and, when both are tightened down, to fix the relative rotative position of the sleeve with respect to the rotatable housing portion 12.

A section through the horizontal supporting shaft 4, the rotary shaft 5 and the upper portion of the intermediate shaft 9 is shown in FIG. 3. The illustrated details of such construction for mounting'the propeller unit and the gearing means 6 is known and need not be more specifically disclosed or require further explanation, since the present invention is not directed to any of the further thereof.

With reference to FIGS. 4a and 4b, cam sleeve 25 with the attached cam 19 is engaged with the roller 23 which in turn is connected on the pressure means 15. In FIG. 4a it should be assumed thatthe symmetry line 40 of the cam 19 coincides with the longitudinal center line or fore-an'd-aft line CL of the boat, while in FIG.

4b the cam is shown rotated through an angle v in relation to the fore-and-aft CL of the boat. FIG. 4a shows the roller 23 engaging a support or bearing surface 20 on the cam 19, the center contact point of this support surface being located on a line A, to 0. In FIG. 4b the support or bearing surface 20 is shown displaced so that the contact point B is located to one-side of the corresponding connecting line A to 0. As will be seen from FIGS. 4a and 4b, the cam 19 is of such a configuration that the roller 23 is moved further away from the center 0 of the cam sleeve 25 with increasing magnitudes of the angle-v away from the line-CL.

It will be seen from a comparison of FIGS. 4a and 4b that the distance between the pin axis A and shaft axis 0 in FIG. 4a is less than the distance between pin axis A and. 0 as shown in FIG. 4b when the cam has been rotatably displaced from its aligned neutral (FIG. 4a) position. This differential distance is taken up by a corresponding axial movement of pressure element 17 in its cylindrical bearing 18 which constitutes aportion of the non-rotatable housing portion 13.

The manner of operation of the mechanism according to the invention will be described. With normal boat steering actions, the rudder-tiller 31 is moved to one side or the other, the guide shaft 32 being rotated to a corresponding degree. This rotation is transmitted through the gearing 33 to the cam sleeve 25, which in turn transmits the steering rotary movement, through the spline joint 27, 28,- to the guide sleeve 26 and then the propeller shaft 11 of the boat and the skeg and propeller shaft housing 41 are thereby subjected to a corresponding degree of rotation.

When the cam sleeve 25 occupies the position illustrated in FIG. 4a, the propeller pressure force creates a moment which is transmitted to the tiller 31 and it is necessary for the person manning the tiller to con stantly counteract this moment in order to hold the vessel on the intended course. As aforementioned, however, the cam sleeve 25 can be adjusted by rotating the same around its center 0. This adjustment is effected by the means for permitting limited relative movement as illustrated and described in connection with FIG. 2. The setting screws 34 are suitably manipulated to turn the guide sleeve 26 relative to the lower portion 12 of a propeller housing 3. When the guide sleeve 26 is rotated, the rotary movement is transmitted through the spline joint 27, 28 to the cam sleeve 25, whereupon the cam 19 is rotated at the same time. For the sake of simplicity of understanding assume that the cam sleeve 25 adopts the position shown in FIG. 4b. The propeller pressure force will then act onpoint B while the force constantly has a direction parallel with the fore-aft line CL of the boat. Thus, a moment is created as a result of the moment arm corresponding to the perpendicular distance from point B to the line A to 0. By making a suitable adjustment of the setting screws 34 which rotates the cam sleeve 25 and guide sleeve 26, the magnitude of this correcting moment can be made equal and opposed to the torque produced by the propeller pressure force, the two moments opposing each other thereby relieving the person manning the tiller of the task of manually counteracting the force acting on the tiller.

In spite of the fact that the aforedescribed compensating mechanism is combined with the tilting and trimming means 14 of the, boat, tilting and trimming of the unit can be carried out in the well known manner, irrespective of the rotative setting of the cam 19 and cam sleeve 25 Applicantclaims priority based on Swedish Application Serial No. 5190/72 filed Apr. 20, 1972.

While the invention has been described with respect to a certain specific embodiment, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover all such modifications and changes'as fall within the true spirit and scope of the invention.

What is claimed as new and what it is desired to secure by Letters Patent of the United States is:

1. In a boat propulsion system wherein a propeller housing is mounted on the stern of a vessel, pressure means mounted between said stern and said housing for tilting and trimming said housing in a vertical plane, said housing when untilted and in operation having a downwardly extending power transmitting intermediate shaft around which a portion of said housing is rotatable for steering and another portion of said housing is non-rotatable, a mechanism for counteracting undesired torques on said rotatable portion comprising: a pressure element disposed for engagement by said pressure means mounted on said non-rotatable housing portion for axial movement of said element therein, a

cam carried on said rotatable housing portion, said cam being operatively associated with said pressure element for movement of said element with respect to said nonrotatable housing portion corresponding to they positioning of said cam, said cam laterally displacing the contact point of the bearing surface on which the propeller pressure is taken up by said pressure element thereby providing a steering moment for compensating for said undesired torque on said rotatable portion.

2. .The system as defined in claim 1 wherein said pressure means for tilting and trimming includes a piston and a cylinder element.

3. The system as defined in claim 2 wherein said nonrotatable portion is provided with a cylinder for mounting said pressure element, and said pressure element is in the form of a piston slidingly disposed within said cylinder.

4. The system as defined in claim 2 further comprising pivotal connecting means for connecting said pressure element to said piston element.

5. The system as defined in claim 4 wherein said pressure element'includes a body portion and roller rotatably mounted thereon for engaging said cam.

6. The system as defined in claim 4 wherein said-nonrotatable portion is provided with a cylinder for mounting said pressure element, saidpressure element being in the form of a piston slidingly disposed within said cylinder.

7. The system as defined in claim 6 wherein said pressure element includes a body portion and roller rotatably mounted thereon forengaging said cam.

8. The system as defined in claim 1 wherein said nonrotatable portion is provided with a cylinder for mounting said pressure element, said pressure element being in the form of a piston slidingly disposed within said cylinder.

9. The system as defined in claim 1 wherein said pressure element includes a body portion and a roller rotatable mounted thereon forengaging said cam.

10. The system as defined in claim 9 further comprising means for rotatably mounting said cam on said r0 tatable housing portion for relative rotation therebetween, and means for fixing said cam in selected rotative position on said rotatable housing portion.

11. The system as defined in claim 10 wherein the shape of said cam is predetermined toprovide that variation of the rotative position of said cam relative to said rotatable housing portion provides variation of the direction and magnitude of said compensating steering moment.

12. The system as defined in claim 1 further compris? ing means for rotatably mounting said cam on said rotatable housing portion for relative rotation therebetween and means for fixing said cam in selected rotative position on said rotatable housing portion.

13. The system as defined in claim 12 wherein the shape of said cam is predetermined to provide that variation of the rotativeposition of said cam relative to said rotatable housing portion' provides variation of the direction and magnitude of said compensating steering moment.

14. The system as defined in claim 10 wherein said fixing means includes screwthreaded adjusting means for adjusting and fixing said relative rotative position of said cam.

15. The system as defined in claim 14 whereinsaid cam is interconnectedly carried on a sleeve member disposed outwardly of said shaft and inwardly of said rotatable housing portion, said rotatable housing portion includes a pair of threaded openings extending laterally of said member, said sleeve member having two opposed portions exposed toward said respective openings and so disposed that when one of said sleeve member portions moves toward either said opening with rotation of said sleeve member with respect to said rotatable housing portion, the other moves away from the other said opening, and wherein said adjusting means includes a pair of setting screws respectively threaded into said openings and respectively contacting said portions of said sleeve member.

16. The system as defined in claim 1 further comprising a guide sleeve surrounding said intermediate shaft and extending between said rotatable and nonrotatable housing portions, bearing means in said nonrotatable housing portion for rotatably mounting said guide sleeve, and means for adjustably fixing said guide sleeve to said rotatably housing portion, said cam being interconnected with and carried on said sleeve.

17. The system as defined in claim 1 wherein said cam is interconnectedly carried on a sleeve member disposed outwardly of said shaft and inwardly of said rotatable housing portion, said rotatable housing portion includes a pair of threaded openings extending laterally of said member, said sleeve member having two opposed portions exposed toward said respective openings and so disposed that when one of said sleeve member portions moves toward either said opening with rotation of said sleeve member with respect to said rotatable housing portion, the other moves away from the other said opening, and wherein said adjusting means includes a pair of setting screws respectively threaded into said openings and respectively contacting said portions of said sleeve member.

18. The system as defined in claim 4 and means for restricting the axial movement of said pressure element with respect to said tiltable housing.

19. The combination, in a downwardly extending propeller housing comprising an intermediate power shaft, an inner housing portion in which said shaft is rotatably disposed, an outer housing portion nonrotatably mounted for tilting on a horizontal transverse axis to the stern of a boat and supporting saidinner housing portion for rotation about the axis of said shaft, said inner housing portion terminating downwardly in a propeller shaft housing, and steering means for rotating said inner housing portion, said inner housing portion being subject to undesired torque tending to rotate said inner housing in a predetermined direction during forward drive of the boat, of means for counteracting such torque comprising: a force transmitting element mounted in said outer housing portion for movement with respect to said outer housing portion in a direction fore and aft of said boat and transversely of said tilt axis, said element having a forward end disposed toward the stern of the boat, means disposed between said stern and said forward end of said element for contacting said forward end and receiving the forward operating propeller reaction force during forward driving of the boat, said last means establishing a predetermined minimum distance between said forward end of said element and said stern, said element having an aftward end exposed within said outer housing portion, means connecting between said inner housing portion and said aftward end of said element for forcing said element forwardly with respect to said outer housing portion in response to steering rotation of said inner housing portion in said predetermined direction, said element applying, during such forward driving of the boat, a force against said inner housing portion through said connection means in a direction tending to rotate said inner housing portion in a direction opposite to said predetermined direction.

20. The combination according to claim 19 wherein said means disposed between said stern and said forward end comprises a hydraulic tilting cylinder and piston assembly.

in a direction forwardly of said boat. 

1. In a boat propulsion system wherein a propeller housing is mounted on the stern of a vessel, pressure means mounted between said stern and said housing for tilting and trimming said housing in a vertical plane, said housing when untilted and in operation having a downwardly extending power transmitting intermediate shaft around which a portion of said housing is rotatable for steering and another portion of said housing is non-rotatable, a mechanism for counteracting undesired torques on said rotatable portion comprising: a pressure element disposed for engagement by said pressure means mounted on said non-rotatable housing portion for axial movement of said element therein, a cam carried on said rotatable housing portion, said cam being operatively associated with said pressure element for movement of said element with respect to said non-rotatable housing portion corresponding to the positioning of said cam, said cam laterally displacing the contact point of the bearing surface on which the propeller pressure is taken up by said pressure element thereby providing a steering moment for compensating for said undesired torque on said rotatable portion.
 2. The system as defined in claim 1 wherein said pressure means for tilting and trimming includes a piston and a cylinder element.
 3. The system as defined in claim 2 wherein said non-rotatable portion is provided with a cylinder for mounting said pressure element, and said pressure element is in the form of a piston slidingly disposed within said cylinder.
 4. The system as defined in claim 2 further comprising pivotal connecting means for connecting said pressure element to said piston element.
 5. The system as defined in claim 4 wherein said pressure element includes a body portion and roller rotatably mounted thereon for engaging said cam.
 6. The system as defined in claim 4 wherein said non-rotatable portion is provided with a cylinder for mounting said pressure element, said pressure element being in the form of a piston slidingly disposed within said cylinder.
 7. The system as defined in claim 6 wherein said pressure element includes a body portion and roller rotatably mounted thereon for engaging said cam.
 8. The system as defined in claim 1 wherein said non-rotatable portion is provided with a cylinder for mounting said pressure element, said pressure element being in the form of a piston slidingly disposed within said cylinder.
 9. The system as defined in claim 1 wherein said pressure element includes a body portion and a roller rotatable mounted thereon for engaging said cam.
 10. The system as defined in claim 9 further comprising means for rotatably mounting said cam on said rotatable housing portion for relative rotation therebetween, and means for fixing said cam in selected rotative position on said rotatable housing portion.
 11. The system as defined in claim 10 wherein the shape of said cam is predetermined to provide that variation of the rotative position of said cam relative to said rotatable housing portion provides variation of the direction and magnitude of said compensating steering moment.
 12. The system as defined in claim 1 further comprising means for rotatably mounting said cam on said rotatable housing portion for relative rotation therebetween and means for fixing said cam in selected rotative position on said rotatable housing portion.
 13. The system as defined in claim 12 wherein the shape of said cam is predetermined to provide that variation of the rotative position of said cam relative to said rotatable housing portion provides variation of the direction and magnitude of said compensating steering moment.
 14. The system as defined in claim 10 wherein said fixing means includes screwthreaded adjusting means for adjusting and fixing said relative rotative position of said cam.
 15. The system as defined in claim 14 wherein said cam is interconnectedly carried on a sleeve member disposed outwardly of said shaft and inwardly of said rotatable housing portion, said rotatable housing portion includes a pair of threaded openings extending laterally of said member, said sleeve member having two opposed portions exposed toward said respective openings and so disposed that when one of said sleeve member portions moves toward either said opening with rotation of said sleeve member with respect to said rotatable housing portion, the other moves away from the other said opening, and wherein said adjusting means includes a pair of setting screws respectively threaded into said openings and respectively contacting said portions of said sleeve member.
 16. The system as defined in claim 1 further comprising a guide sleeve surrounding said intermediate shaft and extending between said rotatable and non-rotatable housing portions, bearing means in said non-rotatable housing portion for rotatably mounting said guide sleeve, and means for adjustably fixing said guide sleeve to said rotatably housing portion, said cam being interconnected with and carried on said sleeve.
 17. The system as defined in claim 1 wherein said cam is interconnectedly carried on a sleeve member disposed outwardly of said shaft and inwardly of said rotatable housing portion, said rotatable housing portion includes a pair of threaded openings extending laterally of said member, said sleeve member having two opposed portions exposed toward said respective openings and so disposed that when one of said sleeve member portions moves toward either said opening with rotation of said sleeve member with respect to said rotatable housing portion, the other moves away from the other said opening, and wherein said adjusting means includes a pair of setting screws respectively threaded into said openings and respectively contacting said portions of said sleeve member.
 18. The system as defined in claim 4 and means for restricting the axial movement of said pressure element with respect to said tiltable housing.
 19. The combination, in a downwardly extending propeller housing comprising an intermediate power shaft, an inner housing portion in which said shaft is rotatably disposed, an outer housing portion non-rotatably mounted for tilting on a horizontal transverse axis to the stern of a boat and supporting said inner housing portion for rotation about the axis of said shaft, said inner housing portion terminating downwardly in a propeller shaft housing, and steering means for rotating said inner housing portion, said inner housing portion being subject to undesired torque tending to rotate said inner housing in a predetermined direction during forward drive of the boat, of means for counteracting such torque comprising: a force transmitting element mounted in said outer housing portion for movement with respect to said outer housing portion in a direction fore and aft of said boat and transversely of said tilt axis, said element having a forward end disposed toward the stern of the boat, means disposed between said stern and said forward end of said element for contacting said forward end and receiving the forward operating propeller reaction force during forward driving of the boat, said last means establishing a predetermined minimum distance between said forward end of said element and said stern, said element having an aftward end exposed within said outer housing portion, means connecting between said inner housing portion and said aftward end of said element for forcing said element forwardly with respect to said outer housing portion in response to steering rotation of said inner housing portion in said predetermined direction, said element applying, during such forward driving of the boat, a force against said inner housing portion through said connection means in a direction tending to rotate said inner housing portion in a direction opposite to said predetermined direction.
 20. The combination according to claim 19 wherein said means disposed between said stern and said forward end comprises a hydraulic tilting cylinder and piston assembly.
 21. The combination according to claim 19 wherein said connecting means comprises a cam connected to said inner housing portion for rotation therewith and bearing against said aftward end of said element.
 22. The combination in accord with claim 20 wherein said assembly comprises one end connected to the stern of the boat and another end pivotally connected to said force transmitting element, and means restricting said movement of said force transmitting element in a direction forwardly of said boat. 